• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.9
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• pp.4119-4124
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• 2011

In a MPC coding using excitation source of voiced and unvoiced, it would be a distortion of speech waveform in case of increasing or decreasing of speech signal amplitude in a frame. This is caused by normalization of synthesis speech signal in the process of restoration the multi-pulses of representation section. To solve this problem, this paper present a method of amplitude compensation(AC-MPC) in a multi-pulses each pitch interval in order to reduce distortion of speech waveform. I was confirmed that the method can be synthesized close to the original speech waveform. And I evaluate the MPC and AC-MPC using amplitude compensation method. As a result, SNRseg of AC-MPC was improved 0.7dB for female voice and 0.7dB for male voice respectively. Compared to the MPC, SNRseg of AC-MPC has been improved that I was able to control the distortion of the speech waveform finally. And so, I expect to be able to this method for cellular phone and smart phone using excitation source of low bit rate.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.1
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• pp.265-274
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• 2019

The paper describes an application of unscented Kalman filter(UKF) for attitude estimation of an unmanned vehicle(UV), which is equipped with a low-cost attitude heading reference system (AHRS). The roll, pitch and yaw required at the correction stage of the UKF are calculated from the measurements of acceleration and geomagnetic field. The roll and pitch are attributed to the measurement of acceleration, while yaw is calculated from the geomagnetic field measurement. Since the measurement of geomagnetic field is vulnerable to distortion by hard-iron and soft-iron effects, the calculated yaw has more uncertainty than the calculated roll and pitch. To reduce the uncertainty of geomagnetic field measurement, the proposed method estimates bias in the geomagnetic field measurement and compensates for the bias for more accurate calculation of yaw. The proposed method is verified through navigation experiments of a UV in a test pool. The results show that the proposed method yields more accurate attitude estimation; thus, it results more accurate location estimation.

• Journal of the Microelectronics and Packaging Society
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• v.31 no.1
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• pp.35-42
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• 2024

Recently, with the miniaturization and high integration of semiconductor chips, the bump bridge phenomenon caused by fine pitches is drawing attention as a problem. Accordingly, Cu pillar bump, which can minimize the bump bridge phenomenon, is widely applied in the semiconductor package industry for fine pitch applications. When exposed to a high-temperature environment, the thickness of the intermetallic compound (IMC) formed at the joint interface increases, and at the same time, Kirkendall void is formed and grown inside some IMC/Cu and IMC interfaces. Therefore, it is important to control the excessive growth of IMC and the formation and growth of Kirkendall voids because they weaken the mechanical reliability of the joints. Therefore, in this study, isothermal aging evaluation of Cu pillar bump joints with a CS (Cu+ Sn-1.8Ag Solder) structure was performed and the corresponding results was reported.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.12
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• pp.1095-1102
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• 2016

This paper presents the results of the design, fabrication and tether test for a gross weight 20 kg tilt-duct VTOL aerial robot. The tilt-duct vehicle, a tri-ducts air-vehicle, which composed of two main tilt ducts for thrust and an aft-fan for pitch attitude control, has been developed as an aerial platform. The research on the air vehicle has been focused on the hover characteristics and controllability to improve the thrust and stability. The tether test for measuring various performance of vehicle and evaluating controllability have been carried out to figure out effects of modified main-prop linkage, actuator, duct configuration and control surfaces.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.49-53
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• 2016

Recently, the use of signal compression methods to improve the efficiency of wireless networks have increased. In particular, the MPC system was used in the pitch extraction method and the excitation source of voiced and unvoiced to reduce the bit rate. In general, the MPC system using an excitation source of voiced and unvoiced would result in a distortion of the synthesis speech waveform in the case of voiced and unvoiced consonants in a frame. This is caused by normalization of the synthesis speech waveform in the process of restoring the multi-pulses of the representation segment. This paper presents an ACFBD-MPC (Amplitude Compensation Frequency Band Division-Multi Pulse Coding) using amplitude compensation in a multi-pulses each pitch interval and specific frequency to reduce the distortion of the synthesis speech waveform. The experiments were performed with 16 sentences of male and female voices. The voice signal was A/D converted to 10kHz 12bit. In addition, the ACFBD-MPC system was realized and the SNR of the ACFBD-MPC estimated in the coding condition of 8kbps. As a result, the SNR of ACFBD-MPC was 13.6dB for the female voice and 14.2dB for the male voice. The ACFBD-MPC improved the male and female voice by 1 dB and 0.9 dB, respectively, compared to the traditional MPC. This method is expected to be used for cellular telephones and smartphones using the excitation source with a low bit rate.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.8
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• pp.649-660
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• 2021

Through analytical method based on S-76 model, the level of rotor hub vibration reduction was analyzed according to higher harmonic actuating by individual blade control. The higher harmonic actuating method for individual blades was divided into a method of generating an additional actuating force from the pitch-link in the rotating part and generating actuating force through the active trailing edge flap control of the blade. In the 100kts forward flight conditions, the hub load analysis was performed by changing the phase angle of 15 degree for the 2P/3P/4P/5P harmonic actuation for individual blades. Through the harmonic actuation results, the sensitivity of the rotor system according to the actuating conditions was analyzed, and the T-matrix representing the characteristics of the rotor system was derived based on this analysis result. And through this T-matrix, optimal higher harmonic actuating condition was derived to minimize hub vibration level for flight condition. In addition, the effect on the performance of the rotor system and the pitch-link load under minimum hub vibration condition, as well as the noise influence through the noise analysis were confirmed.

• Journal of Internet Computing and Services
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• v.19 no.6
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• pp.1-7
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• 2018

This paper present an 8kbps ACLMS-MPC(Amplitude Compensation and Least Mean Square - Multi Pulse Coding) coding method integrated with ACFBD-MPC(Amplitude Compensation Frequency Band Division - Multi Pulse Coding) and LMS-MPC(Least Mean Square - Multi Pulse Coding) used V/UV/S(Voiced / Unvoiced / Silence) switching, compensation in a multi-pulses each pitch interval and Unvoiced approximate-synthesis by using specific frequency in order to reduce distortion of synthesis waveform. In integrating several methods, it is important to adjust the bit rate of voiced and unvoiced sound source to 8kbps while reducing the distortion of the speech waveform. In adjusting the bit rate of voiced and unvoiced sound source to 8 kbps, the speech waveform can be synthesized efficiently by restoring the individual pitch intervals using multi pulse in the representative interval. I was implemented that the ACLMS-MPC method and evaluate the SNR of APC-LMS in coding condition in 8kbps. As a result, SNR of ACLMS-MPC was 15.0dB for female voice and 14.3dB for male voice respectively. Therefore, I found that ACLMS-MPC was improved by 0.3dB~1.8dB for male voice and 0.3dB~1.6dB for female voice compared to existing MPC, ACFBD-MPC and LMS-MPC. These methods are expected to be applied to a method of speech coding using sound source in a low bit rate such as a cellular phone or internet phone. In the future, I will study the evaluation of the sound quality of 6.9kbps speech coding method that simultaneously compensation the amplitude and position of multi-pulse source.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.285-286
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• 2011

Wind turbine system is converting wind energy into electric energy. In nature, torque of the blade is nonlinear function. To get a high quality electric power, system needs control of blade angle. The control of a blade is divided into a stall regulation type and a pitch control type. Pitch control type is more expensive and complicated, but it can make torque of the blade in accordance with variable wind. This paper shows 2MW pitch control system's hardware and electric part.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.6
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• pp.98-108
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• 1994

An assessment of a mathematical method of synthesing tire tread pitch noise spectra is studied. The method is based on the summation of phasors and the calculated spectra are conveniently generated as computer printout in the form of bar graph. The technique, its usefulness, its limitations and the implications of using such a model are discussed. This paper presents a basic study on optimum pitch arrangement for prediction and control of tire tread pitch noise in constraint condition relatied with tire properties, thus enabling optimum tread pitch arrangements to be determined at the design stage, by application of old tire tread pitch simulation.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.546-549
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• 2009

풍력을 이용한 풍력발전기의 효율적 전력변환 시스템을 연구개발하기 위해서는 바람의 특성을 실내에서 정확히 구현할 수 있는 모의시험장치인 시뮬레이터가 요구된다. 모의시험장치는 바람을 받아 회전하는 블레이드 대신 풍속 값을 입력하여 전동기가 발전기에 토오크(torque)를 공급하게 된다. 모의시험장치를 설계하고 구현에 있어서 중요한 요소는 블라인드의 관성시정수와 축소모델인 5.83kW 모델 발전기 설계제작 그리고 고효율의 전력변환장치 설계 및 인버터 특성 알고리즘 구현이다. 본 논문은 2MW Gearless형 풍력발전기 KBP-2000M을 400:1 축소하여 제작한 모의실험장치에 최고의 출력 파워를 얻도록 Pitch Control 알고리즘을 적용한 측정 결과를 소개한다.